AZ Alkmaar chief Max Huiberts has hit out at the amount of loan players from Chelsea and Manchester City in the Eredivisie.
NAC Breda enjoy a partnership with Manchester City, while Vitesse lean heavily on Chelsea.
Huiberts is fed up with the arrangements and told Voetbal International: "The situation is unhealthy.
"The rules should be tightened."
However, KNVB spokesman Daan Schippers said: "The KNVB has not received any signals from clubs who are concerned about this trend. As soon as it arrives, it is discussed amongst the technical team, but that is not yet the case."